1. Field of the Invention
The present invention generally relates to automatic guidance of vehicles and, more particularly, to the precision execution of docking or parking maneuvers based on visually detectable locations to precisely guide the vehicle to a desired location.
2. Description of the Prior Art
Various approaches have been made to automatic control of numerous aspects of vehicle operation with many differing objectives such as safety, avoidance of operator fatigue and the like which have met with varying degrees of success. For example, for control of automobiles, various arrangements have been proposed to maintain a minimum separation distance between vehicles and regulate speed and/or provide guidance on, for example, high-speed highways. Automatic guidance systems have been employed with substantial success to maintain a chosen course for aircraft and seagoing vessels. For rail traffic, particularly commuter trains in which the vehicle movement is constrained to the locus of movement defined by the tracks, position locating arrangements are known to control the position at which a vehicle may be brought to a stop (e.g. adjacent a particular position along a platform) as well as maintaining train separation through block monitoring and control.
However, known applications for non-rail vehicle guidance are generally limited to use where exact vehicle position is not particularly critical and the control maintains a particular mode of operation or movement of the vehicle rather than executing a particular maneuver. For example, known systems may be used to maintain a given compass heading at a given speed for ships and aircraft or, for automotive vehicles, to follow a track-like locus of detectable features (e.g. a painted stripe on the roadway) at a given or controllable speed.
In this latter regard, efforts continue toward developing an automated highway system to guide and control speed of vehicles during trips over extended distances. However, until recently, the automation of particular and precise maneuvers and the accurate automated positioning of a vehicle relative to some fixed facility (e.g. bus stop, wheelchair access ramp, loading dock, etc.) has not been seriously addressed. While some devices have been developed (essentially as vision aids for the vehicle operator of large vehicles where certain views are restricted from the location of the operator) any maneuver for precise positioning of the vehicle is generally done manually or, at most, by following markers, magnets, buried cables or the like in the roadway. Such devices are subject to substantial wear and damage unless they are buried and buried devices are subject to electromagnetic interference (e.g. reinforcing steel in the roadway).
Therefore, neither type of system has proven particularly reliable and maintenance costs are substantial in any event. In particular, if tracking of such devices is lost, it is extremely difficult to reacquire, during which autonomous guidance of the vehicle will not be possible.
Sonar arrangements have also been attempted to provide vehicle guidance or separation from obstacles or other vehicles. However, sonar-based systems are very limited in range and subject to interference from ambient noise, wind, doppler effects and the like. Even for highly directional sonar systems, the area covered and the possible sources of noise increase greatly with distance. Therefore, sonar-based systems are not able to develop high confidence factors for target acquisition or to acquire targets at a range supporting control of change of course or speed at moderate rates.
During the same period of time, however, the need for precise maneuvering and positioning of vehicles has become increasingly important. For example, the requirement for provision of access for handicapped persons to public transportation often requires the placement of the vehicle so that curbs will not need to be negotiated. Ground clearance of buses means a substantial difference in height of a step above a roadway as compared with a curb and may thus easily become a source of injury. The increased use of trucks for transportation of goods in recent years requires accurate placement of the truck relative to a loading dock in order to avoid accidents and injuries to personnel and impediments to rapid loading and unloading of cargo.
Additionally, such maneuvers and the size and configurations of buses or trucks often obscures or prevents a line of sight being maintained from the vehicle operator to a fixed structure which defines the vehicle position to be achieved. Wear or damage to portions of the vehicle (e.g. tires, steering gear, body panels and the like) often results from contact of the vehicle with such fixed structures, especially curbs. Furthermore, the accurate positioning of a vehicle for public transport or the transportation of goods must often be carried out dozens if not hundreds of times each day. Therefore, damage to the vehicle is a relatively regular occurrence.
To be effective, positioning must be repeatably accurate within a small tolerance of several inches or less and with an angular alignment of a few degrees or less. This accuracy must often be accomplished with one of several maneuvers, some of which may require reversal of vehicle direction in areas potentially congested with vehicular and/or pedestrian traffic. While sufficient accuracy has been approached with devices placed in or on the roadway, in addition to the drawbacks alluded to above, such arrangements allow essentially no departure from a fixed path or alternative maneuvers.
In summary, while various approaches to autonomous vehicle guidance and other automatic controls have been under development for a number of years, no system is yet available which can repeatably achieve accurate positioning and alignment of a vehicle or automatically control the vehicle through a maneuver necessary to achieve such positioning. Current systems also are incapable of supporting variant or different maneuvers to achieve such positioning of a vehicle and are generally expensive and difficult to install and/or maintain. Additionally, it is desirable that a system having such a capability be compatible and fully integratable with arrangements for providing autonomous guidance control suitable for a highway environment. Further, guidance systems suitable for roadway vehicles have not employed techniques which are applicable to other modes of transport such as marine vessels (including submarines) or aircraft.